The present invention relates generally to antenna systems. More particularly, the present invention is directed to an antenna system designed for multi-channel, broadband applications. The antenna of the present invention has a construction that achieves low windloads, and allows a feed system of the antenna system to be easily accessed for service.
Under the rules of the Federal Communication Commission, by the year 2006, television broadcasters are required to transition from current National Television System Committee (NTSC) antenna systems to digital television (DTV) antenna systems. NTSC antenna systems are analog systems, and during operation of analog NTSC systems only one television transmission signal is transmitted per channel.
DTV is a new type of broadcasting technology. DTV antenna systems transmit the information used to make television pictures and sounds by data bits, rather than by waveforms, as performed by NTSC systems. With DTV, broadcasters will be able to provide television programming of a higher resolution and better picture quality than what can be provided under the current analog NTSC antenna systems. In addition, DTV broadcasters will be able to transmit more than one signal per channel, and thus, deliver more than one television program per station.
All current analog TV broadcasts will be phased out by the end of 2006. During the transition to DTV, television broadcasters are faced with having to transmit on two channels simultaneously, (NTSC and DTV).
Historically, panel antennas are utilized for multi-channel, wideband/broadband applications. One disadvantage of panel antennas is that they exhibit higher windloads than conventional single channel antennas, such as the slotted coaxial type, due to the size of the panel assemblies attached to an antenna mast. Further, the size of the panel antennas limit the amount of radiating assemblies that can be positioned around a mast, and consequently, the amount of flexibility in varying the overall azimuth pattern of panel antennas.
Wideband cavity-backed antennas are also utilized for multi-channel broadband applications. However, there are disadvantages associated with wideband cavity-backed antennas. For example, one exemplary conventional waveguide cavity-backed antenna utilizes a radiator element having a xe2x80x9ct-shapedxe2x80x9d geometry. The xe2x80x9ct-shapedxe2x80x9d radiator element is costly to manufacture because a significant amount of machining labor is required to construct the xe2x80x9ct-shapedxe2x80x9d radiator element.
Further, the design of the exemplary conventional wideband cavity-backed antenna is such that the assembly of the waveguides form the antenna mast-like structure, without use of a mast. The design also includes a feed system that is positioned within the hollow space formed when the waveguides are assembled together.
However, one drawback of the exemplary conventional wideband cavity-backed structure is that when the feed system requires service, the antenna has to be removed from its supporting structure and disassembled to access the feed system. Accordingly, interruption in television service to customers who are receivers of television signals transmitted by the antenna requiring service is prolonged by the time required to take down and disassemble the antenna to reach the feed system.
Further, the design of the exemplary conventional wideband cavity-backed antenna requires a capacitive disk, which is coupled to the xe2x80x9ct-bar shapedxe2x80x9d radiator element and separated from the waveguide by an air gap, along with a grounding rod to match the impedance of the transmission line to the impedance of the radiator element.
However, the air gap limits the amount of power that the radiator element is able to accommodate. The air gap, like a dielectric, is only able to accommodate a limited amount of power without breaking down. If the air gap breaks down and allows current to flow between the transmission line and the waveguide, the undesired current could potentially damage the radiating element.
Accordingly, it would be desirable to provide an antenna that may be utilized for multi-channel, broadcast applications that exhibits low windloads.
It would also be desirable to provide an antenna that allows for greater flexibility in varying the overall azimuth pattern of the antenna.
In addition, it would also be desirable to provide a multi-channel, broadband antenna that has high power handling capabilities.
Further, it would be desirable to provide a multi-channel, broadband antenna that allows for simplicity in impedance matching.
Moreover, it would be desirable to provide a multi-channel, broadband antenna that is cost-effective to manufacture and simple to service.
In one aspect of the present invention, an antenna system is disclosed that includes a mast, waveguides positioned about the mast, and a feed system positioned external to the mast and between adjacent waveguides.
In another aspect of the present invention, an antenna apparatus is disclosed that includes a means for transmitting signals, a means for guiding the signals from the transmitting means, wherein the guiding means is coupled to the transmitting means, a means for supporting the guiding means, wherein the guiding means is positioned on an external surface of the supporting means, and a means for feeding the transmitting means, wherein the feeding means is coupled to the external surface of the supporting means.
In yet another aspect of the present invention, a method for transmitting signals is disclosed that includes dividing an antenna into an upper half and a lower half, and feeding the antenna off from a center line of the antenna, such that the lower half of the antenna is fed ninety degrees out of phase with the upper half of the antenna.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.